The Quest to Create a Test for Marijuana Impairment

Marijuana is playing a larger role in the daily lives of many Americans. Massachusetts is one of eight states, as well as the District Columbia, where recreational use of marijuana is now considered legal. Additionally, twenty states have legalized the use of medical marijuana. There remain questions about how the use of marijuana should be regulated. While motor vehicle operators are prohibited from driving a vehicle while impaired by marijuana, there is no accurate test for determining whether an individual has consumed marijuana. Among this uncertainty about the impairment of motor vehicle drivers in Massachusetts who might have taken marijuana, there is currently a case pending from a Massachusetts state court that will likely provide some illumination about what approach Massachusetts will take to these challenges created by detecting marijuana impairment.

The Danger Presented by Marijuana Use

Although many (but not all) studies have found that marijuana impairs an individual’s ability to safely operate a motor vehicle, the impairment to drive appears to be slight and the equivalent of an individual with a blood alcohol content level between .01 and .05 percent. A researcher at the Institute of Transport Economics went so far as to compare driving while under the influence of marijuana as the equivalent of driving in the darkness. There is also not a direct relationship between the amount of marijuana one consumes and how impaired a motor vehicle driver becomes. Blood levels of THC, the chemical component of marijuana that impairs individuals, rise quickly after smoking and decline rapidly in the hours afterwards.

Field Tests to Assess Driver Impairment

In addition to disagreements about the danger of driving a motor vehicle while under the impairment of marijuana, there is also a lack of an established method for determining whether an individual is unable to drive. While standard field sobriety tests have proven to be effective in assessing whether an individual has operated a motor vehicle with a blood alcohol content above the legal limit, there is not test that has proven as effective for detecting the presence of marijuana in motor vehicle operators. Even though law enforcement lacks a validated test to determine marijuana impairment, there are numerous mobile applications that have been created over the last few years to assess an individual’s marijuana impairment.

Standards for Marijuana Levels in the Blood of Drivers

Currently, 18 states contain laws that draw a relationship between driving under the influence to the levels of THC that are found in a motor vehicle driver’s blood. While some states prohibit driving a motor vehicle with blood that contains amount of THC, other states have THC thresholds that are modeled after the .08 blood alcohol content limit. The delayed time between being pulled over and being transported to a hospital for a blood test, however, can result in inaccurate results. 31 states have taken the approach of prohibiting driving while impaired by marijuana. Establishing that a motor vehicle operator is impaired by marijuana, however, has proven to be particularly challenging.

The Role of Law Enforcement Officers in Detecting Marijuana

There is some evidence suggesting that law enforcement officer might not be adequately trained to determine whether an individual is impaired or high from marijuana. Several states including Montana, New Jersey, and Vermont have directly ruled that law enforcement officers are not equipped to make assessment about whether a motor vehicle operator demonstrates that signs of someone who is impaired from marijuana. In response to this perspective about the inability of motor vehicle operators to assess marijuana impairment, some law enforcement agencies have begun to use drug recognition experts to determine whether motor vehicle operators are impaired by marijuana.